Hi lwatson, if you do not have any addons then the correct patch is 1.8.0.25 which you can download from here http://www.aerofly.com/www/downloads.html I am not sure if you're referring to model downloads written for version 1.9.x.x AFPD, but if thats your question, you can still run the models in version 1.8.x.x AFPD by doing the below modification to the tmd file:

Go to the aircraft directory C:\Program Files\IPACS\AeroFly Professional Deluxe\aircraft and open the aircraft file.
Look for the .tmd file and open it with a text editor like notepad or word

Now you need to alter this line in the .tmd file:

// aerofly professional --------------------------------------------------------
//
// file: xxxxxxx.tmd
// version: 1.9.0 <<<<<<<<ALTER THIS LINE TO: // version 1.8.0
//
// type: 20
// lock: 0
//
// -----------------------------------------------------------------------------

Then click save